There has long been a need for a self-contained, easy to assemble, low cost, universal, and safe umbrella fan. The design constraints associated with such an umbrella fan include the fact that the umbrella canopy is often lowered when not in use by the action of a slide which surrounds the umbrella pole operated by a crank mechanism which also surround the umbrella pole. Thus, any useful after-market umbrella fan assembly must be able to be easily coupled by the consumer to the umbrella pole between the crank mechanism and the umbrella canopy slide.
U.S. Pat. No. 6,017,188 discloses a fan assembly permanently disposed on the umbrella pole above the slide. Accordingly, this assembly is not designed as an after-market fan which can be used in conjunction with a wide variety of umbrellas previously purchased by consumers.
U.S. Pat. No. 5,007,811 discloses a fan assembly supported on an umbrella pole below the umbrella slide but requires, in each embodiment, bearings supporting the integral rotatable drive ring to which the fan blades are attached. In one embodiment, the large drive gear of the rotatable drive ring and the drive ring itself have a slot therethrough for receiving the umbrella shaft. To compensate for this slot, either two opposing drive pinions are required (one on either side of the slot) or, instead, a special gear key is required to fill the gap in the drive gear, and, in that embodiment, only one drive pinion is required.
The '811 patent also purports to show an embodiment where the drive gear and the drive ring are split and pivot about a hinge. Still, even in this embodiment, the bearings supporting the rotatable drive ring are still required as part of the fan assembly housing. Since, in the design of the '811 patent, the drive ring is an integral part of the fan motor housing, the resulting structure is necessarily complex and difficult to manufacture at a low cost. Finally, the '188 patent notes that the fan assembly of the '811 patent is unstable.